<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>固定定位</title>
  <style>
    body {
      height: 2000px;
    }

    .box {
      width: 200px;
      height: 200px;
      background: #000;
    }
    .title{
      background-color: aquamarine;
      position: sticky;
      top: 0;
    }
  </style>
</head>

<body>
  <div class="box"></div>
  <div class="title">导航栏</div>
</body>

</html>